when encountering an unknown peer in received gossip, rather than
ignoring the entire gossip we create a placeholder Peer. This has
version 0 and uid 0, which means it will be replaced by any complete
peer information subsequently received via gossip.
This is mostly a matter of moving some files, changing package names,
changing some imports, and changing some type references.
We duplicate the odd constant & global var, and the intmac/macint
functions, since neither 'router' or 'mesh' nor, really,' common' are
a natural home for them.
Matthias Radestock